Optical Wireless Communications - from the space to the chip.

OPTICAL WIRELESS COMMUNICATIONS
“From the space to the chip”
OQCG Short Seminar Series
March 2014

My Snapshot
PhD (2009) @ UPV - “Wireless comms integration on Optical networks (RoF,
UWB, WiMAX, WDM, PolMux, …)”
• Previous Research topics about OWC
– Atmospheric turbulence effects on outdoor OWC
– Hybrid systems FSO/RF
– OWC for intelligent transport system
– Others : LTE over fiber, Indoor VLC systems (TV/Internet streaming)
Indoor POF+VLC
• Common topics:
– Optical transceivers
– New efficient modulation schemes
– Optical transmission
March 2014 - OQCG Seminars

Optical Wireless Communications
• Ancient as the human kind
– beacon fires, smoke, ship flags or semaphore telegraph
– Photophone 1880 A.G.Bell
• Laser revolution  1962 MIT Lincoln Labs OWC GaAs light source over 30
miles for TV transmission
– Beam divergence problems, atmospheric effects, the fibre appears at 70’s to
solve those problems
– OWC relegated to satellite interlinks, IrDA, some military applications.

Optical Wireless Communications
• Advantages: Low Cost, license free, high BW access solution
– Light sources : LASER – LED – OLED
• Problems: atmospheric losses, turbulence, and pointing errors
• Many applications
– Optical angular moments for Quantum Cryptography
– Satellite optical networks
– Wearable interaction
– Indoor low-cost communications
– Enterprise/campus connectivity
– Video surveillance and monitoring
– Backhaul for cellular systems
– Broadcasting
– Redundant link and disaster recovery

Ultra-long and long range OWC
• Sports events (F1)
• Campus, MAN networks
(Cablefree, LightPointe ...)
• Security and defence
communications
(CASSIDIAN, EADS, ...)

Air-to-Ground FSO
• Air-to-ground FSO quantum-
key distribution
communication
(Nature Photonics 7, 382–386 (2013))
(Photos: DLR)
Speed of 290 km/h at a distance of 20 km
or 4 mrad/s

Space-ground FSO
• Laser Communications Relay
Demonstration LCRD
• High bandwidth geo-sync to
ground optical link
– Downlink: 1.2 Gbps
– Uplink: 1.2 Gbps
– LCRD Payload Flight in 2017 on
Loral Commercial Satellite
• Bidirectional low Earth orbit-
to-ground optical link
– 2 Mb/s UL and 50 Mb/s DL
M.W. Wright et al. , 26 September 2011, SPIE
Newsroom.
(Photos: NASA and SPIE)

FSO networks
• Intra-satellite
• Campus networks
• FSO link needs line of
sight (LOS)
• Link Obstacles??
– Buildings, fog,
turbulence...
– No connection!
• A mesh topology as a
solution??
(Photos: ESA)

OWC comms and adverse channel effects
Mitigating Turbulence Effect
• Spatial Diversity Solutions
• Relay-Assisted FSO Networks
• Hybrid RF/FSO Links
OWC impairments are
derived from the channel
variations
• Adverse Channel Effects
– Background Radiations
– Pointing Errors
– Atmospheric Loss
– Atmospheric Turbulence

Medium range OWC
• IR indoor comms
– Irda extended (Giga-IR)
• Vehicle-2-Vehicle comms
– Volvo Intelligent road concept
• Visible Light Comms - VLC
– Li-Fi, internet
– LED shopping assistant

LED and VLC
• RGB • Blue Chip + Phosphor
- Well-known technology
- Limited use due to difficulties in
RGB balancing
- Phasing out in lighting industry
- Wide modulation bandwidth
- Popular for today general lighting
industry
- Standardised for illumination and
communications
- Limited modulation bandwidth
White Light emission

LED and VLC
• LED -> PN junction -> Small transit time
• Modulation BW from 3 MHz to 20 MHz
• Enough for communications?
– Equalisation techniques
• Up to 40 Mb/S @ 400 Lux, 2m range [1] using multi-
tone equalisation at transmitter
– Complex modulation
• PAM
• OFDM  OMEGA FP7 project (2011) (Siemens/HHI)
has demonstrated 84 Mbps OFDM/QAM – over 3m
[2]
– MIMO as a diversity technique
• 4x4 50 Mb/s [3]
– Gigabit VLC = EQ + OFDM + MIMO [4]
[1] H. Le-Minh et al., "High-Speed Visible Light Communications Using Multiple-Resonant Equalization", IEEE PTL 15 (20), Jul. 2008
[2] http://www.youtube.com/watch?v=AqdARFZd_78
[3] A. Burton et al. “Experimental Demonstration of 50 Mb/s Visible Light Communications using 4×4 MIMO,” IEEE PTL, March 2014
[4] G. Cossu et al. “2.1 Gbit/s Visible Optical Wireless Transmission”, ECOC 2012 , P4.16

LED and VLC
• Mobility
– NLOS must work
– Channel reflections
– Smart receiver
• Diffuse receiver: direct and
reflected path
• Multiple receivers: best signal
• LOS vs NLOS: GAIN 20 dB
• Light dimming
Key effects
– The SNR is no longer the advantage
– Signal could be discontinued
Main dimming technologies
– Driving current reduction  lower
PTx and SNR
– Pulse width modulation (PWM) 
Signal disruption
TransmitterReceiver
AWGRTO
Spectrum
analyzer
0% 50% 75% 100%PWM MSR
30 Mb/s
50 Mb/s
70 Mb/s
By A. Burton et al. To be published in 2014

LED VLC integration
• Video streaming over LED link
• 10 Mb/s
• Nov. 2013

LED - OLED
• Solid-state light emitting diode (LED)
– Compact, cheap, powerful
– 50% light
– More than 50,000 hours lifespan
• Organic light emitting diode (OLED)
– Flexible and bendable panel
– Extensively used in high-end display products,
– HDTV and Smartphone

OLED Devices

OLED Current State-of-Art
• Efficiency
– 100% internal quantum efficiency (Fraunhofer IPMS – COMEDD, 2012)
– Brightness 2.000 cd/m², 5mm thickness (Verbatim Velve, 2012)
– 120 lumen (~table lamp) (Philip Lumiblade GL350, 2012)
– 80 lumen/watt with 20.000 hours of lifetime (LG, 2012)

OLED Current State-of-Art
• Applications
– Dominant in high end Smartphone display products: Super-AMOLED,
(Samsung Galaxy S3 phone, 2012)
– 55 inch OLED HDTV (Samsung Electronics, 2012)
– 6 inch E-paper on plastic (XGA, 14 gram, 0.7mm thickness), (LG, 2012)
– Solar OLED car (BASF, 2012)
– Flexible AMOLED display (Samsung patent, 2012)
– None of the commercial applications is for communications!

Electrical Characterisation
• For lighting
– Large panel  better for illumination
 larger capacitor value
• For communications
Larger capacitor value  slow response
Rp - electrode contact resistance
Rd - diode resistance
C - diode capacitance

OLED – Techniques
Aim: High-speed OLED VLC system (Mbit/s over kHz bandwidth)
• Analogue Equalisation
• Decision Feedback Equalisation
• OFDM / QAM
• ANN
– P. A. Haigh, Z. Ghassemlooy, and I. Papakonstantinou, "1.4 Mb/s White Organic LED Transmission System using
Discrete Multi-tone Modulation," IEEE Photonics Technology Letters, vol. PP, pp. 1-1, 2013
– Paul Anthony Haigh, Francesco Bausi, Zabih Ghassemlooy, Ioannis Papakonstantinou, Hoa Le Minh, Charlotte Fléchon,
Franco Cacialli, "Visible light communications: real time 10 Mb/s link with a low bandwidth polymer light-emitting
diode," Opt. Express 22, 2830-2838 (2014);
.

Short and ultra-short range OWC
• Wireless body area networks
– Wearables :
– Toys, dresses and LED interactions
• Disney research [1]
• Low data rate
• Device integration
• OWC Underwater comms
– Offshore platforms sensor networks [2]
• Water scattering , attenuation by refraction,
[1] Stefan Schmid, Giorgio Corbellini, Stefan Mangold, and Thomas R. Gross. 2013. LED-to-LED visible light communication networks. In Proceedings of the
fourteenth ACM international symposium on Mobile ad hoc networking and computing (MobiHoc ’13). ACM, New York, NY, USA, 1-10.
[2] J. A. Simspson et al. “Smart Transmitters and Receivers for Underwater Free-Space Optical Communication”, IEEE JSAC, 5 (30), June 2012
Photos: Disney ©

Ultra-short range OWC
• Chip to Chip comms
– Couplers fibre to chip
• Grating couplers, tappering, …
• Future sensor networks (O’Brien, Oxford)

Future of OWC
• Ultra short range  depends on photonic chip
• Short-range  depends on consumer adoption (Li-Fi, wearables, …)
• Medium range  niche market, established, future depends on the
channel impairments solutions and the deployment of OWC networks
under extrem situations
• Long-range / ultra long  Satellite is OWC the solution?
– VALIDATION OF TURBULENCE MITIGATION TECHNIQUES FOR
HIGH DATA RATE OPTICAL LINK - ESA Invitation To Tender 7386
– NASA last issues
– DLR and quantum tranmission
• New OWC SME will engage the big players?

Latest news on OWC
“Smartphone concept incorporates LiFi sensor for receiving light-based data” ,
OLEDCOMM at CES 2014
“Pure LiFi transmits data using light (video)” at MWC 2014
“Charge and receive data with light: TCL Communication/ALCATEL ONETOUCH
and Sunpartner Technologies announces the first fully integrated solar
smartphone” at MWC 2014
“High-Speed Stock Traders Turn to Laser Beams” at WSJ FEB 2014
“Extreme Test for the ViaLight Laser Communication Terminal MLT-20 – Optical
Downlink from a Jet Aircraft at 800km/h”, EADS & DLR Dec 2013
“NASA Historic Demonstration Proves Laser Communication Possible ” by NASA
Nov 2013, Lunar Laser Communication Demonstration or LLCD

MWP & OWC?
QKD & OWC?
POF + ACCESS + OWC + …?
And now?

Optical and Quantum Communication Group (OQCG)
iTEAM Research Institute
Universitat Politecnica de Valencia, Spain
http://joaquinperezsoler.blogs.upv.es/
joapeso@upv.es // Gscholar // @joakin_perez
DR JOAQUIN PEREZ
POSTDOCTORAL RESEARCH FELLOW

Optical Wireless Communications - from the space to the chip.

Optical Wireless Communications - from the space to the chip.

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